This invention concerns a method of manufacturing polyester fibers with good adhesion to rubber.
Polyester fibers, represented by polyethylene terephthalate, have excellent physical and chemical properties and are very useful fibers which are mass produced industrially and are widely used in various fields. They are also a very suitable material for reinforcing rubber.
However, polyester fibers have the great defect that they are inferior in adhesion to rubber compared to polyamide fibers such as nylon 6, nylon 6,6, etc., which are also typical industrial fibers.
Thus, when polyamide fibers are simply treated with a resorcinol-formaldehyde-rubber latex (RFL) adhesive, they have good adhesion with rubber, but in the case of polyester fibers, even when this RFL treatment is performed, good adhesion cannot be obtained.
For this reason, many attempts have already been made to improve the adhesion of polyester fibers to rubber. Typical methods for doing this are: (1) when treating the raw cord textile with the RFL treatment (the so-called "dipping treatment"), it is first pretreated with an adhesive such as an epoxy compound, an isocyanate compound, an ethylene urea compound, etc., and then treated with RFL or RFL mixed with an esterophile ingredient such as a novolak resin, or 2,6-bis(2',4'-dihydroxyphenylmethyl)-4-chlorophenol, known by the trade name "Pexul", and (2) an adhesive such as an epoxy compound, an isocyanate compound, etc., is added at the yarn stage followed by dip-treating with RFL. The former method, although it does give the desired adhesiveness to some degree, has the defects that it requires a large quantity of adhesive, and the treatment method is troublesome, which tends to increase the cost. The latter method, although it has the practical advantage that, like the polyamide fibers, the later dip treatment can be performed with RFL alone, has the defect that the essential adhesive function is somewhat insufficient. Consequently, particularly in the latter method, a new problem is created that, in order to increase the adhesion, the method of treating the yarn itself must be performed under conditions which deviate greatly from the practical range. The concentration of the adhesive used in treating the yarn is markedly increased; the heat treatment conditions are made extremely severe, etc.